The US Consulate at the American Embassy in London is canceling visa appointments with the following email:
Information for visa applicants regarding novel coronavirus: As of Tuesday March 17, the United States Embassy in London is cancelling routine immigrant and nonimmigrant visa appointments. We will resume routine visa services as soon as possible but are unable to provide a specific date at this time. The MRV fee is valid and may be used for a visa application in the country where it was purchased within one year of the date of payment. If you have an urgent matter and need to travel immediately, please follow the guidance provided at www.ais.usvisa-info.com/en-GB, or call +44 20 3608 6998 to request an emergency appointment.